The invention comprises a fuel pump for supplying fuel to injection systems of internal combustion engines or, alternatively, to carburetors therefor. The pump is preferably driven by an electromotor and comprises two pump units disposed in series as a two-stage pump. A fuel supply at a low pressure but with a high output is produced on the suction side of a second pump unit by a first pump unit which is disposed upstream of the second unit and which delivers its high output as a gas-free fluid to the second pump unit, which actually feeds the fuel supply to the engine.
The present invention comprises an improvement upon known fuel pumps of the single stage type. The readily evaporable fuels currently in use, such as gasoline, frequently contain 20% by weight of constituents, such as isopenthane, which boil at temperatures of 40.degree. C. Such constituent boiling causes gas bubbles to be formed in fuel pumps of known type, with the result that from 40.degree. C. upwards the proper pressure build-up in the pump may no longer be ensured. Measures known in the prior art for alleviating these conditions, such as producing an excess pressure in the fuel tank or incorporating the fuel pump in the fuel tank, are relatively costly, susceptible to breakdowns, or incompatible with specific safety regulations.